1. Field of the Invention
This invention relates in general to an ozone production unit and more specifically to a discharge type ozonizer for producing ozone by causing oxygen to come into contact with an electrical discharge field.
2. Description of the Related Art
The conventional discharge type ozonizer mainly employs the glass tube as a dielectric element but lately the ceramic discharge type which utilizes ceramic material as the dielectric element has spread into wide use and occupies a share of the ozonizer category. The following problems must be resolved in order to improve ozone generating efficiency in ceramic discharge type ozonizers.
In discharge type ozonizers the greater part of the electrical power applied in the discharge is converted into heat. When the temperature from this heat energy raises the temperature in the discharge section of the ozonizer, the ozone which was generated there is broken down by the heat with the resulting problem that less ozone is generated.
Consequently a cooling jacket has been proposed as shown in FIG. 4 and FIG. 5 for conventional ceramic discharge ozonizers. In the example of FIG. 4, on one surface of the ceramic dielectric element 2 is placed a ground terminal 5, and a water cooling jacket 7 by way of an insulator 6 on the outer surface of the ground terminal 5. Cooling water flows into one end of the water cooling jacket 7 from the inlet 7a and flows out through the other end by way of the outlet 7b. Cooling of the ceramic dielectric element 2 is thus performed by the ground terminal 5. The discharge electrode 1 is mounted at a prescribed gap relative to the ceramic dielectric element 2 by means of the insulating spacer 6a. This discharge electrode 1 and the ground terminal 5 are connected to the high voltage power supply 21 and high voltage, high frequency power is applied between the ground terminal 5 and the discharge electrode 1 to form a discharge field in the space between the ceramic dielectric element 2 and the discharge electrode 1.
A gaseous material is made to flow through the discharge field. In the example in FIG. 5, a metal discharge electrode 1 is mounted opposite the surface of the ceramic dielectric element 2 just as in FIG. 4. However FIG. 5 differs in that a water cooling jacket 9 is mounted on the outer surface of the metal discharge electrode 1 by means of the insulating cover 6b.
Enlarging the ozonizer size is difficult because of the thin ceramic plate generally used in ceramic discharge ozonizers. Therefore, in order to obtain a specified amount of ozone, several small ozonizer units must be combined together. In the conventional cooling water jacket method, this combination of ozonizer units requires complex cooling water piping and the consequent problem of distributing equal amounts of coolant water in this complex piping system to each ozonizer unit.
Among further problems in the conventional cooling water jacket method is a phenomenon referred to as chattering that occurs within the cooling water jacket when cooling water flows a minimal distance from inlet 7a to outlet 7b causing variations in the cooling efficiency. Another problem is that when air or gas bubbles enter the cooling water, air tends to collect in the upper part of the cooling water jacket so that a localized portion is not cooled and in extreme cases may lead to damage of the ceramic plates. Also, in the cooling water jacket method the heat from the discharge section is cooled by means of the ceramic dielectric element 2 and the ground terminal 5 so there is large resistance to heat propagation and cooling efficiency is therefore poor.
Still further problems are that ceramic discharge ozonizers easily become dirty compared to glass tube discharge ozonizers, with the consequent drawback that performance drops. This problem is caused by the large surface roughness of the ceramic dielectric when compared with the glass tube discharge type.